Known drive power transmitting systems for vehicles include chain-driven front wheel drive shafts and constant velocity joints connecting the front wheel drive shafts to front wheels, as disclosed in JP-U-60-72304.
A front wheel drive shaft disclosed in JP-U-60-72304 has a tubular shape and is rotatably supported by a case via a plurality of roll bearings. The drive shaft serves as an outer ring of a constant velocity joint.
Ball joint units are swingably connected to opposite ends of an inner peripheral portion of the front wheel drive shaft. Each ball joint unit is connected to a front wheel via a relay axle. A sprocket is attached to an outer peripheral portion of the front wheel drive shaft.
When a tread or distance between the left and right front wheels is reduced, a joint angle or an angle between the ball joint unit and the front wheel drive shaft inevitably becomes large with the result that the front wheel can not vertically move by a large amount. If a distance between the left and right ball joint units is made small, the joint angle can be made small even when the tread is reduced. As a result, the amount of vertical movement of the front wheels can be increased.
Further, it is troublesome to assemble to a case the front wheel drive shaft previously assembled with the left and right ball joint units connected to the left and right relay axles.
Furthermore, for removal of the sprocket from the front wheel drive shaft, it is necessary to remove from the case an assembly composed of the front wheel drive shaft, the left and right ball joint units and the left and right relay axles and then to remove the ball joint units and the relay axles from the front wheel drive shaft. Such a removing operation would adversely affect maintenance of the sprocket.
There is a demand for a drive power transmitting system for a vehicle capable of being assembled and undergoing maintenance operation more efficiently as well as providing a small joint angle of the constant velocity joint for improving transmission efficiency.